It is often necessary to conduct bottom hole pressure surveys in fluid wells to obtain data which can be used by analysts to determine the characteristics of the wells and producing formations. This is especially important in the case of injection wells, where continual monitoring of the well conditions is essential in determining whether the injection operation will continue unaided or whether a well stimulation program should be undertaken.
Since the pressure near the formation face most accurately reflects actual conditions in the well, it is common practice to use a bottom hole shut-in tool to seal the pressure gauge from fluid in the wellbore above it. This exposes the gauge only to the fluid below the level of the shut-in tool, thus avoiding errors in the analysis caused by wellbore storage. This procedure is effective, however, only to the extent that the shut-in tool is capable of completely closing off the tubing to the passage of fluid. If the shut-in tool and the seating nipple conventionally provided to receive the shut-in tool are misaligned, or if sediment or other debris is trapped between the usual O-ring seal and the seating nipple, the fluid passageway in the tubing often is not effectively sealed, resulting in inaccurate readings.
It would therefore be desirable to have a bottom hole shut-in tool which is capable of effecting a seal even under conditions of misalignment and trapped debris. It would also be desirable for such a shut-in tool to be simple in design and easy to use.